Histoplasmosis Risk Factors

Although anyone who inhales the fungal components (spores, mycelia) may
develop histoplasmosis, unless a large number of fungal organisms or repeated
exposure to the fungi occurs, disease is usually infrequent in healthy people.
However, infants, children, the elderly, and those with chronic lung disease are
at risk. Immunodepressed patients (for example, cancer or
AIDS patients) are at
the highest risk for severe histoplasmosis.

Histoplasma capsulatum lives in acidic, damp environments that contain organic
material. High concentrations of the fungus occur in caves where bats or birds
reside, and the fungi are in the soil. Bats, but not birds, can become infected
and spread the fungi in their feces. Most outbreaks occur when construction or
renovation projects disturb and aerosolize dust containing the fungi so people
who participate in or live near such projects are at higher risk for
histoplasmosis.